Breast cancer is the most common cancer of American women and the leading cause of cancer-related death among women aged 15-54. Early detection of breast cancer through mammography can lead to a high probability of cure. However, because of several inherent limitations of film as a recording device for the mammographic image, conventional screen-film mammography is limited in its ability to detect subtle cancers, especially in patients with radiodense breast tissue. Digital mammography offers a means of overcoming these limitations. This application's overall objective is the transfer of the successful results of more than 10 years of research on the development and evaluation of high resolution CCD detectors for macromolecular crystallography to digital mammography, resulting in a modular, scalable, high performance system for full breast imaging. The project is a collaborative effort between the University of Virginia Health Sciences Center and the Rosenstiel Center at Brandeis University. The proposed mammographic detector, based on a proven design and comprised of components whose manufacture is well within current commercial fabrication capabilities, will provide sensitivity and resolution exceeding that projected for full breast systems currently under development by several equipment manufacturers. The full detector will be composed of an array of detector modules, each of which contains an X-ray phosphor deposited directly onto a fiber optic taper, which is in turn bonded to a CCD array. The detector will provide a digital alternate to analog screen/film systems, exhibiting higher detective quantum efficiency (DQE), a larger dynamic range, superior linearity, and near realtime readout. Because of its higher DQE and low noise, the proposed detector will enable quantum-limited operation over a larger range of X-ray fluence than do current screen/film systems, thereby allowing reduced glandular dose for the same image quality. Specific developmental tasks are as follows: TASK 1: Basic performance characteristics of a single module under mammographic conditions will be measured. Characteristics to be measured will include gain, sensitivity, and the system modulation transfer function (MTF), noise power spectrum (NPS), and DQE as a function of spatial frequency. TASK 2: Software for data acquisition and display, and algorithms for correction of geometric distortion and nonuniformity of detection efficiency for images from a single module will be developed. TASK 3: Composite images formed from multiple single module subimages will be evaluated. Basic imaging characterization will be performed on the composite images, with particular attention to image quality at the subimage boundaries. TASK 4: The diagnostic imaging capability of the multi-module detector will be evaluated through ROC analysis, comparing the imaging capabilities of the CCD array detector with those of the screen-film systems currently in use at the UVa Diagnostic Center for Women. TASK 5: During the third year, a 4-module (24 cm x 24 cm) clinical prototype array detector will be constructed, using the optimized module design. TASK 6: The basic and diagnostic imaging properties of the clinical prototype detector will be evaluated, as described above.